Though
scholars at the turn of the 20th century understood that Christianity was
heavily influenced by Mithraism, there is a recent trend among Christian apologists
and revisionist academics to deny this historical debt to paganism. As a case
in point, Christian historian Justo Gonzales makes the following remark to
refute earlier scholarship on the subject in his 1970 book “A History of
Christian Thought”, Volume I:

"Concerning
the relationship between the mystery cults and Christianity, scholarly opinion
has varied. During the first two or three decades of the twentieth century, it
was thought that the mystery religions constituted a unity based on a common
'mystery theolgoy,' and that Christianity was simply
one of them, or at most, a distinct religion is which the influence of the
mysteries was greatly felt. According to the scholars of that time [e.g., W. Bousset, A. Loisy and R. Reitzenstein], Christianity had taken from the mysteries
its rites of initiation----baptism, its sacramental meals---communion; its
ascending stages of initiation----the orders; and a multitude of details
needless to enumerate. But since then, a careful study has been made of the
mysteries, and the conclusion reached by almost all scholars is that there was
no such thing as a common 'mystery theology'---at least in the first century of
our era. Quite the contrary, the mystery cults differed one from another so
much that it is difficult even to explain the term 'mystery religion.'
Moreover, the mysteries seem not to have reached their full development until
the second and third centuries, which is the time when the majority of their
characteristics in common with Christianity appear. It follows that such traits
can be more easily explained as the influence of Christianity on the mysteries
than the opposite, the more so when we learn that already in this period the
pagan cults tried to imitate some of the characteristics of the dynamic new
faith.”

Gonzales
based his refutation on a chronological argument. It is a common belief that
Mithraism did not enter the Roman world until well after Paul’s lifetime.
Alison B. Griffith, for example, says that “the evidence also indicates that at
least some inhabitants(or Rome and its port city Ostia) knew about Mithraism as
early as the late first century CE, but that the cult did not enjoy a wide
membership in either location until the middle of the second century CE.”
Similarly, the Britannica observes that “there is little notice of the Persian
god in the Roman world until the beginning of the 2nd century, but, from the
year AD 136 onward, there are hundreds of dedicatory inscriptions to Mithra.” Even much earlier, in the beginning of the 20th century,
Albert Schweitzer argued that Apostle Paul could not possibly have had contact
with what we know as the Roman mystery religion of Mithraism since it did not
flourish until after his death around 67 AD.
TRAVELER23 has also argued in this forum that “therefore, it is historical nachronism to argue that Paul took his understanding of the
Eucharist from Mithraism.”

However,
this line of argument breaks down completely when we realize that the mystery
religion that Paul was exposed to in his hometown Tarsus, in the province of Celicia, was NOT Roman Mithraism but Persian Mithraism. Celicia was at the outskirts of the former Persian Empire,
right at the border of the Greco-Roman world and the Persia world. In fact,
Encyclopedia Britannica provides support of this thesis of mine. For it
explains how Mithraism was marginalized in its native land, Persia, because of
its central ceremony, the sacrifice of the bull. Since Zoraster
denounced bull sacrifice, it became an abhorrence for every Zoroastrian. In
fact, according to Britannica, by the time Alexander the Great conquered the
Persian Empire around 330 BC, the worship of Mithra
could no longer be found in Persia. Effectively, Mithraism was forced to
migrate due to pressure from Zorastrianism.
Britannica says that “local aristocrats in the western part of the former
Persian Empire(the region around Tarsus) retained their devotion to Mithra. The kings and nobles of the border region between
the Greco-Roman and the Iranian world still worshipped him.”

This
would explain why the center for Mithra worship moved
from Persia to Paul’s birthplace, Tarsus, which was a thriving intellectual hub
and a melting-pot of religions in the first century BC.

To
conclude, while it is historically true that Mithraism did not flourish in Rome
until the beginning of the second century AD, the first contact between
Mithraism and Christianity was most likely to have happened during the lifetime
of Paul in the Hellenistic city of Tarsus, which was an old seaport with a long
history of Mithra worship. It is highly likely that
Paul, in an attempt to woo the Gentile believers, deliberately incorporated
elements of Mithraism into his brand of Gentile Christianity. Even today,
remnant of Mithraism is most evident in the Christian Eucharist, which involves
the eating of the flesh and drinking of the blood of a deity(Christ). Since the
drinking of blood has always been an abomination in Judaism, it is much more
logical to attribute this ritual to Mithraism, which had a much similar ritual.
In addition, the setting of the birthday of Christ on December 25th, which was Mithra birthday, and the shifting of the day of worship
from Friday(Sabbath) to Sunday(the day of the Sun) are further reminders of
Christianity’s debt to its pagan predecessor.